This year's Heritage Open Days, which starts on Thursday and runs until Sunday, has free events within half an hour of the vast majority of the population. Culture24 takes a look at some of the regional highlights coming up this weekend…

South-EastThe scope for snoopers in Oxford has been substantial enough for planners to create their own programme of events. "The extraordinary range of places to see and things to do over the weekend is amazing," admits Debbie Dance, Director of the Oxford Preservation Trust. "We could not have arranged this without a huge swell of goodwill and support. It just proves what a wonderful city we all live in."

Among the highlights are Oxford Detectives – following in the footsteps of Morse and Lewis across some of their old Oxford stomping grounds – and boat trips from Hythe Bridge. Call 01865 252037 for more details and to book, or visit Oxford Open Doors for more events.

South-WestThe English Riviera might not be able to go under that name if it wasn't for Brokenbury, the biological sewage treatment works for Torbay.

Check out the surprisingly intricate matter of keeping sea water bearable at the centre courtesy of Southern Water on Thursday and Friday (10am-12pm, pre-booking required, call 01392 443020).

Find out why The English Riviera is relatively sewage-free

MidlandsBagot's Castle, in Baginton, near Coventry, is believed to have been built in 1397 by Sir William Bagot, although the site was originally home to a castle in the early 12th century.

By the 16th century it was in ruins, and by the 18th century only the moat and rubble remained. The rectangular keep, a stair turret, five vaulted chambers and floor tiles were found during a 15-year excavation from 1933, and the results will be open to the public on Saturday and Sunday (10.30am-5.30pm).

EastWillis Country Head Office doesn't sound like a glamorous building, but it's actually the youngest construction in England to have been given Grade I-listing thanks to sheer glass walls and a kidney-shaped design.

Head to Ipswich town centre to see why (Saturday and Sunday, 10am-2pm).

Redcliffe mines run three acres under Bristol

WestBetween the 15th and 18th centuries, a set of mines extended three acres under the Redcliffe area of Bristol.

Tours of some of them will take place on Saturday (10am-4pm, bring torches and suitable footwear.)

North-EastVisitors to one of the Hull branches of Boots might rarely look up and see the stars, but above their chemist of choice stands the Neptune Inn, which served as the poshest hotel in town after being built at the end of the 18th century.

Overlooking the Georgian facades of Parliament Street, the "spectacular" Adamesque-style ceiling of this little-known gem will welcome crowds on Saturday (11am-4pm).

Stockport Air Raid Shelters

North-WestOrganisers in Stockport say their Air Raid Shelters saved residents during the "dark days" of the Blitz during World War II, although it's unlikely locals got much more light in the labyrinth of tunnels they escaped to, which still run under the town centre.

Limited-number tours will be taking place on Friday and Sunday (1pm-5pm, last entry 4pm, call 0161 474 4444 for details).